1. Field of the Invention
The present invention relates to a method and machine for making artificial snow and more particularly to an improved method and heater devise useful with all kinds of snow making machines to prevent compressed air line freeze-up and thereby benefit making large quantities of high quality, granular snow.
All snow making machines are provided with a nucleator where compressed air mixes with pressurized water to form a spray of ice crystal nuclei. The heater devise of the present invention serves to pre-heat the compressed air entering the nucleator. One type of snow making machine useful with the present heater device provide an air flow generator disposed inside a housing of the machine to propel the spray of ice crystals leaving the nucleator through a water shower. The water shower is provided by a water injector that baths the ice crystals. As the water coated ice crystals travel through the ambient air, the water freezes to form ice granules. Another type of snow making machine is referred to as an air/water type. This machine does not have an air flow generator or a water injector. Instead, the compressed air and pressurized water are expelled out the nucleator propelled solely by their combined forces. This type of snow making machine requires large volumes of compressed air for proper functioning.
Regardless of the type of snow making machine used, the heater device of the present invention insures that the compressed air flows from the main air compressor through the compressed air hydrant and conduit system to reach the nucleator at a sufficiently warmed temperature so that any humidity present in the air will not freeze and render the compressed air system inoperative prior to the air mixing with the pressurized water in the nucleator. Thus, by heating the compressed air upstream from the nucleator, the air hydrant heater of the present invention benefits snow production in existing air systems for all types of snow making machines wherein the compressed air has a relatively high moisture content. This negates the need to dehumidify the compressed air or provide the compressed air with an anti-freeze additive to insure continued nucleator operation at any snow making temperature.
2. Prior Art
Preventing humidity from freezing in the compressed air system supplied to the nucleator of a snow making machine can be a troublesome and vexing problem. In any snow making machine, it is imperative that the compressed air line remain open and provide for sufficient flow volume to the nucleator where the compressed air mixes with pressurized water to form the spray of ice crystal nuclei expelled from the nucleator. It is this spray that travels through the freezing ambient atmosphere to form ice granules.
In a ski resort having multiple ski runs with a plurality of snow making machines positioned at strategic locations along the runs, each snow making machine, regardless of whether it is provided with an air flow generator and a water injector or if it is an air/water type, must be fed with pressurized water and compressed air. The compressed air is usually provided by a hose that connects to a main air hydrant supplied by a central air compressor. The compressed air can leave the compressor at temperatures approaching 200.degree. F. In some cases, the compressed air is moved through an air cooler that lowers the air temperature to between about 60.degree. F. to 80.degree. F. Even at these cooled temperatures, air can hold a relatively large volume of humidity.
The main air hydrant leaving the compressor is often buried to a point where the air hoses feeding the respective snow making machine connects to the air hydrant. Thus, what additional air cooling that does take place between the compressor and the point where the air hydrant surfaces from below ground is usually not a problem. Air line freeze-up occurs, if at all, in the compressed air system between the point where the air hydrant surfaces and the nucleator, or between the air cooler and the nucleator, as the case may be, and especially along the length of the exposed portion of the air hydrant and compressed air hose connection. The reason for this is that these parts are usually made of heat conductive materials, such as metal to facilitate connecting the air hose to the air hydrant.
As previously mentioned, one technique that has been practiced extensively by the prior art is to flow the compressed air through an after cooler before the air is moved to the compressed air hydrant. This can be an extremely expensive solution which renders it impractical for the vast majority of ski resorts. Another technique practiced by the prior art has been to inject an antifreeze solution, such as methanol into the compressed air leaving the compressor. However, in addition to being expensive, this is dangerous. Still another prior art method used to prevent air line freeze-up is to periodically switch the hoses used as the compressed air hose and the pressurized water hose feeding off the respective air and water hydrants. That way, the pressurized water is used to blow any build up of frozen humidity out of the air line. The problem with this method is that it requires the constant attention of an operator and still does not solve the problem of humidity freezing in the air hydrant itself.
The air hydrant heater of the present invention thus provides an economical, reliable and easily operated device for preventing compressed air line freeze up in all types of snow making machines. In that respect, the present air hydrant heater preferably connects to the compressed air main and since both the air main and air hydrant heater are of a thermally conductive material, heat energy generated by the air hydrant heater is conducted to the air main to there warm the compressed air and help prevent freeze-up. Additionally, the air hydrant heater warms the air flowing therethrough to a sufficient degree so that what cooling that does take place downstream is not sufficient to freeze up the air line and the nucleator.